Cast iron fireplaces lose their finish over time. With each use, the heat degrades the original finish. Soot and other byproducts of burning wood also cause a cast iron fireplace to become dirty, masking the finish even more. Cast iron is a poor adhesion material, so you can't use just any paint to refinish it. Restoration requires the right materials and plenty of old-fashioned elbow grease.
Clean the interior of the cast iron fireplace out with a fireplace or stove tool set, using the brush and shovel to take out any burnt wood and ashes. Vacuum the inside out after all large pieces are removed.
Wash the cast iron's exterior with a water-based degreaser and steel wool pad. Then wipe down water excess with clean, damp cloths to remove any degreaser residue. Let the cast iron dry for about four hours.
Put down dust sheets around the cast iron fireplace and move al other furniture away. Create a barrier with dust sheets between the cast iron and other home decor. Open the windows to promote good ventilation.
Put on eye protection and a dust mask. Apply a coat of self-etching primer aerosol to the exterior, holding the aerosol can about 8 inches away from the fireplace. Let this dry for at least four hours or as long as recommended by the manufacturer.
Spray on a coat of high-temperature enamel spray, maintaining the same 8-inch distance as with the primer aerosol can. Spray evenly over the cast iron fireplace's surface, creating a smooth application coat. Allow this to dry for four to five hours or according to the manufacturer's directions. Remove the dust sheets for the fireplace and surrounding areas and restage your furniture and decor.